Graft Copolymers Of Polyethylene Research Articles

Graft copolymers of polyethylene by atom transfer radical polymerization

Poly(ethylene-g-styrene) and poly(ethylene-g-methyl methacrylate) graft copolymers were prepared by atom transfer radical polymerization (ATRP). Commercially available poly(ethylene-co-glycidyl methacrylate) was converted into ATRP macroinitiators by reaction with chloroacetic acid and 2-bromoisobutyric acid, respectively, and the pendant-functionalized polyolefins were used to initiate the ATRP of styrene and methyl methacrylate. In both cases, incorporation of the vinyl monomer into the graft copolymer increased with extent of the reaction. The controlled growth of the side chains was proved in the case of poly(ethylene-g-styrene) by the linear increase of molecular weight with conversion and low polydispersity (Mw /Mn < 1.4) of the cleaved polystyrene grafts. Both macroinitiators and graft copolymers were characterized by 1H NMR and differential scanning calorimetry. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2440–2448, 2000

Reactive processing of polyethylene and polyethylene–ethylene/propylene/dicyclopentadiene blends under static and dynamic conditions

Dicumyl peroxide induced reactive melt processing of polyethylene (PE) in a shear mix at 170°C in the absence or presence of selected acrylic monomers (acrylic acid, ethyl acrylate, and butyl acrylate) has been studied. The acrylic graft copolymers of PE showed development of higher shear stress compared with the control PE when studied rheologically in a plate and cone viscometer at 160–190°C. All the modified PE products retained the pseudoplastic flow behaviour of PE. Measure of rupture shear parameters and of thixotropic and relaxation behaviour of the different modified PEs and of the control PE were also evaluated and compared. The observed effects and unexpected trends were analysed and interpreted.The comparative effects of sulphur vulcanisation of polyethylene–ethylene/propylene/dicyclopentadiene terpolymer (PE–EPDM) blends by static and dynamic techniques were also studied using both a conventional curative system and a silane curative system. Rheometric studies indicated development of a co-continuous phase morphology for the 30/70 PE–EPDM blend. For a given blend, cured under given conditions, tensile strength and elongation at break at 25°C were higher for vulcanisates obtained statically than for those obtained dynamically, while the corresponding modulus values followed the opposite trend. The conventional curative usually cured at a higher rate. The property differences from static and dynamic vulcanisation are explained in the light of the differences in the developed morphology.

Synthesis of Polyethylene-g-polystyrene and Polyethylene-g-poly(p-methylstyrene) Graft Copolymers

This paper describes a new method to prepare polyethylene graft copolymers, such as polyethylene-g-polystyrene and polyethylene-g-poly(p-methylstyrene), with a relatively well-controlled reaction mechanism. The chemistry involves a transformation process from the metallocene copolymerization of ethylene and p-methylstyrene to the anionic living polymerization of styrene or p-methylstyrene. The metallocene catalysis produces poly(ethylene-co-p-methylstyrene) random copolymers with molecular weight distribution (Mw/Mn) of about 2.5. The following selective metalation reaction of p-methylstyrene units in the copolymer and the subsequent anionic “living” graft-from polymerization were effective to produce polymeric side chains with well-defined structure. Both graft density and graft length can be controlled by p-methylstyrene content in the PE backbone, metalation reagent, and the quantity of monomer used in the graft-from reaction. In the bulk, the individual PE and PS segments in the graft copolymers are...

Polyethylene graft copolymers with a liquid crystalline component in the side chains

AbstractAn ethylene‐vinyl acetate copolymer (EVA) was chemically modified by the introduction of pendent thiol groups (EVA‐SH) suitable for chain transfer. The resulting copolymer was grafted with 4‐phenylazophenyl 4‐(4‐acryloyloxybutoxy)benzoate, a liquid crystalline monomer (LCM), initiated by AIBN. Grafting was performed at LCM/EVA‐SH mass ratios of 10, 5, 2 and 1 in the feed. The grafting degree, i.e., the fraction of LC polymer in the graft copolymer, ranged from ca. 5–30 wt.‐%. The thermal transitions were investigated by DSC, pointing at marked microphase separation between LC and polyethylene moieties. The anisotropic properties of the graft copolymers were confirmed by cross‐polarized light microscopy. All the samples showed birefringence at 140°C, some only on shearing however.

ChemInform Abstract: Synthesis of Graft Copolymers of Polyethylene: Grafting of Fluorinated Model Compound Oligomers

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of graft copolymers of polyethylene: grafting of fluorinated model compound oligomers

The condensation reaction of perfluorinated amines on to (succinic anhydride)-HDPE (high-density polyethylene) graft copolymer have been studied. Four different amine structures have been synthesized which have been analyzed by 1H NMR spectroscopy GC-MS methods. Model structures of succinimide and succinamic acid have been synthesized with each amine and analyzed by FT-IR spectroscopy in order to determine the structure of the copolymer obtained. A scale of reactivity has been deduced as a function of the amine structure. Grafting levels of copolymer have been determined by elemental analysis of fluorine.

Rate of adhesion of bovine T-cells to polyethylene-based particles.

Rate of adhesion/detachment of bovine T-cells to or from polyethylene-based materials was studied according to a mechanism consisting of consecutive reversible and irreversible adhesion. Polyethylene and a graft copolymer of polyethylene and poly-2-hydroxyethylmethacrylate were used. Time dependence of concentration of free and adhered T-cells can be expressed by the mechanism. The detachment rate hardly changed with temperature, but the rate of adhesion increased with increasing temperature. The activation energy of the latter was 20-40kJ/mol.

Kinetic features and mechanism of oxidation of cyclohexene in the presence of heterogenized Co(II) on the surface of polyethylene

1. The catalyst prepared by attachment of Co(II) ions on granules of the graft copolymer of polyethylene with acrylic acid effectively catalyzes liquid-phase oxidation of cyclohexene, ensures chain propagation (in the initial stage of the reaction) due to activation of oxygen by Co(II) ions, and catalytic decomposition of hydroperoxide with emission of radicals into the volume. 2. Chain breaking takes place both in bimolecular recombination of alkenyl peroxide radicals in the bulk and with the participation of cobalt ions on the surface of the catalyst (linear breaking). 3. The reactions of complexing and decomposition of cyclohexenyl hydroperoxide with Co(II) and Co(III) acetylacetonates were studied. The corresponding complexing constants, initiation constants, and order of the reactions were estimated. 4. The structure of the heterogeneous catalyst was studied by IR spectroscopy. Free carboxyl groups are present on the surface near the catalytic sites, and chemisorption of hydroperoxide molecules on these groups results in a high local concentration of hydroperoxide in the region of the active sites regardless of its concentration in bulk. The constancy of the rate of initiation and the rate of oxidation of the olefin is a consequence of this.

Synthesis and properties of the graft copolymers of polyethylene and fluorine-containing polymers

The properties of graft copolymers of PE with polyvinyl fluoride (PVF) and polyvinylidene fluoride (PVDF) synthesized by radiation-chemical methods have been investigated. A study was made of graft polymerization rates in relation to temperature and to other factors including the nature of grafted monomers, the presence of vapours of various liquids in the systems and the PE films thickness. Structural transitions and changes in the physico-chemical and mechanical properties of the initial and the irradiated PE and the fluorine-containing graft copolymers were investigated by methods of X-ray and IR analysis and by determination of extreme angles of wetting and by study of density, swelling and thermostability. It was found that grafting of the selected fluorine-containing polymers to PE increases its heat resistance, thermostability, light-fastness and stability towards the action of organic liquids. In addition, the tensile strength of the studied materials was increased.

Mechanical properties of graft copolymers of polyethylene and acrylonitrile obtained by the inhibited graft polymerization method

Etude comparative des copolymeres greffes avec ou sans addition d'inhibiteur de degradation thermooxydante

Stress–strain properties of graft copolymers of polyethylene and acrylic acid

Stress–strain properties of graft copolymers of polyethylene and acrylic acid

Evaluation of the type of grafting and composition of polyethylene graft copolymers by the combination of IR spectroscopy and attenuated total internal reflection

IR Transmission spectroscopy and attenuated total internal reflection (ATR) methods were used to study spectra of N-acryloyl-β-alanine and acrylamide grafted to polyethylene. The composition of graft copolymers was evaluated. Constants of copolymerization were determined: r 1=0·8±0·1 and r 2=1·1±0·3, respectively.

Graft copolymer modification of polyethylene–polystyrene blends. I. Graft preparation and characterization

The preparation and characterization of styrene–low-density polyethylene graft copolymers for addition to blends of polyethylene and polystyrene to improve blend mechanical properties is described. The direct method of grafting with 60Co radiation was employed using the polyethylene in pellet form. This approach gave good grafting efficiency with maximum yields limited to about 1 g of styrene reacted per gram of polyethylene. Excessive crosslinking at radiation doses beyond about 1 mrad was detrimental to the melt processibility of the graft. Crystallinity, dynamic mechanical properties, morphology, and stress–strain behavior of the grafts were examined and compared with melt blends of similar composition in order to better characterize the material produced.

Ionic reverse osmosis membranes of grafted polyethylene

AbstractMembranes of graft copolymers of polyethylene with poly(sodium styrene sulfonate), poly(4‐vinylpyridinium methyl bromide), and poly(sodium acrylate) were prepared by using the technique of peroxide grafting. The reverse osmosis characteristics of the membranes were examined as a function of grafting yield. In these membranes, the grafting can be considered as a process of introducing ionic sites, and it depends on the conditions of the grafting reaction, such as monomer concentration and temperature. However, the overall reverse osmosis characteristic is not only dependent on the number of ionic sites introduced but also on the swelling capability of the membrane. Consequently, the salt rejection of grafted membrane of a fixed graft yield depends on the conditions of the grafting reaction. All grafted membranes which have grafting yields above a certain value behave as normal ionic polymer membranes, and their interrelationship of salt rejection and water permeability follow the general dependence found for ionic polymer membranes.

The permeation of gases through modified polymer films. IV. Gas permeability and separation characteristics of graft copolymers of polyethylene and teflon FEP films

AbstractThe effects of grafting styrene and acrylonitrile onto polyethylene and Teflon FEP films on their gas permeation and separation properties were investigated. The time‐lag method was used to determine the permeability, diffusion, and solubility coefficients of nitrogen and methane gases in the grafted films. The separation factors of nitrogen—methane gas mixtures were measured by gas chromatography. Structural and morphologic changes in the modified films were examined by density, differential scanning calorimetry, and infrared measurements. Attempts were made to relate these changes to the gas permeation and separation characteristics of the films. Modification by graft copolymerization resulted in slightly improved separation factors; however, the permeability and diffusion coefficients decreased. The experimental permeability and diffusion coefficients for gas mixtures were in good agreement with those of the pure components and could be predicted by single gas permeability and diffusion coefficients.

Bipolar Ion-Exchange Membranes Prepared from Blends of Graft Copolymers

Abstract Bipolar ion-exchange membranes were prepared from graft copolymers of polyethylene (PE). Powders of styrene-grafted PE (I) and 4-vinylpyridine-grafted PE (II), or powders of ethyl acrylate-grafted PE (III) and II were blended in various proportions and melt-pressed to films. Ion-exchange groups were then introduced by the sulfonation (100%), alkaline hydrolysis (100%), or N-methylation (80–90%) of the blend polymer films. Although, in the titration curves of bipolar membranes, pH regions which apparently resemble the isoelectric point of polyampholytes appeared, no behavior based on the interaction between acidic and basic groups was indicated in the survey of their physico-chemical properties. The dependency of the concentration potential of the membranes (Em), containing one kind of ionized group, on the mole fraction of the group (Fi) is not remarkable. On the other hand, the Em of the membranes containing both positively- and negatively-charged groups is strongly dependent on Fi, because of the additive contribution of the oppositely-charged groups to the potential. The bi-ionic potential of the membrane, EK–Li, was found to be a function of Em⁄|E0|(|E0| is the absolute value of the concentration potential for ideal permselective membranes) in the cases of both I-II and II-III.

Some problems of adhesion of polyethylene graft copolymers

Some problems of adhesion of polyethylene graft copolymers

The permeability of some graft copolymers of polyethylene to gases and vapors

AbstractGraft copolymers of polyethylene were prepared by gamma irradiation of polyethylene films immersed in the appropriate monomer. The majority of gas permeability measurements were made by Barrer's high vacuum technique; others were made by measuring volumetric change as a function of time. Sorption isotherms were obtained by using a quartz helix microbalance. Temperature dependent permeability constants have been obtained for permeation of oxygen, nitrogen, and carbon dioxide through styrene, acrylonitrile, and vinylpyridine grafted to low‐density polyethylene. Permeability constants at 25°C. have also been determined as a function of water vapor partial pressure for the above systems. Some values for permeation of carbon dioxide through styrene grafted to high density or linear polyethylene are also given. Organic vapors studied were methyl bromide and isobutene, permeability constants at 0°C. being determined for styrene and acrylonitrile–polyethylene graft copolymers as a function of organic vapor pressure. The data show clearly that permeation through acrylonitrile and vinylpyridine–polyethylene grafts is primarily a diffusion process, while in permeation through polyethylene–styrene grafts, there is also a crystallite solution effect. Percentage grafts varied from 0 to 100 parts monomer per 100 parts by weight polyethylene.